Back in the day, a lot of kids in my area used to have bottle cap collections. In recent years, though, I think that hobby has become somewhat frowned upon by parents. Probably has something to do the many sharp serrated edges, and the fact that discarded bottle caps usually support vast thriving colonies of bacteria. But that's just a guess...

... plus the fact that most soft drinks now come in plastic bottles, with glass reserved almost exclusively for beer. Apparently there just aren't enough hard-drinkin' youngsters out there these days to sustain the hobby.